1. Field of the Invention
The present invention relates to an image processing device and an image processing method. More specifically, the present invention relates to an image processing method and an image processing device to perform correction processing on image data such as digital picture images.
2. Description of the Related Art
As printers and digital cameras become more sophisticated in performance and available at lower cost in recent years, the printing of digital pictures is gaining popularity among general users. In response to this background, it is widely practiced to correct original images using many application programs and printer driver's functions to allow them to be printed to the users' preference.
A major image correction method currently available involves raising an overall lightness and chroma to make an image look more vivid and crisp. It is also a well known method to detect gamuts of so-called “memory colors” such as colors of skin, grass and sky and to render only the memory colors more vivid or correct them into more preferred colors. These methods can be performed in a variety of ways: the user or operator manually executes the methods; an image is analyzed to execute the methods automatically; the user specifies a mode for their execution; or additional information such as photographing information is analyzed for their automatic execution.
Japanese Patent Application Laid-Open No. 06-121159 discloses a technique that detects memory colors and decides, based on the amount of the memory colors occupying an image, whether or not to correct the memory colors.
Japanese Patent Application Laid-Open No. 2001-292333 discloses a technique which corrects foreground colors according to background colors, by taking advantage of the characteristics of human visual perception in which the colors of foreground changes according the background images.
Japanese Patent Application Laid-Open No. 2003-134354 discloses a technique which determines the number of pixels having a chroma higher than a predetermined level and, for those images with a greater number of such pixels than a predetermined value, corrects a tone of portions having a high chroma.
However, with these techniques disclosed in the above patent documents, there are cases where images which look preferable to human perceptions can not be obtained even after they have undergone the above correction processing.
As one cause for this problem, the inventors of this invention have found that the human preference for “showiness” of colors changes according to concentrations of highly chromatic color areas in an image. Here, quantities associated with the “showiness” or include chroma, lightness, contrast and hue. When highly chromatic color areas are concentrated, they look too heavy or too showy to human eye. Thus, the “showiness” should be kept low. Conversely, where the highly chromatic color areas are dispersed, they look vibrant and vivid in the image if their level of showiness is enhanced.
With the techniques disclosed in the above patent documents, however, since the concentration of highly chromatic color areas is not detected, the “showiness” is not properly corrected. It is therefore not possible to form images that look most preferable to human perception.